Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/25/24
Area Forecast Discussion
National Weather Service La Crosse WI
1047 PM CDT Sun Mar 24 2024
.KEY MESSAGES...
- An impactful winter storm expected to affect the area into
Tonight.
- Monday and Monday Night will be warmer with periodic rain
showers.
- Colder air will move into the region on Tuesday. Rain will
change over to snow. Little snow accumulations expected.
&&
.UPDATE...
Issued at 455 PM CDT Sun Mar 24 2024
At 2145z, KARX reflectivity depicts a very impressive 40-50dbz band
of precipitation moving through northeast Iowa quickly to the
north. As it approaches, heavy snow with very large dendritic
flakes have been noted on IA plowcams and by observers at onset
of heavy precipitation. The thermodynamics within this band of
precipitation are very complex with KARX correlation coefficient
at this time showing a profound melting layer working in from
the south associated with strong mid-level warm air advection
with a 700-900mb jet approaching upwards of 60 kts in recent RAP
soundings at KDEH. Consequently, this has enabled a stronger
forcing regime allowing for very heavy precipitation rates (even
a couple of lightning flashes noted as well!) within this band
albeit some of it may be slightly overexaggerated by radar due
to melting layer contamination. As the band progresses through,
strong warm air advection aloft will allow for precipitation to
switch over from snow to rain as noted in several observations
across northeast Iowa, with a period of heavy sleet being
possible in spots. Heavy snow within the band could produce
rates of 1-2" per hour leading to quick slushy accumulations on
roadways. As a result, deciding to hold onto the Winter Weather
Advisory south of I-90 in northeast Iowa for now.
&&
.DISCUSSION...
Issued at 122 PM CDT Sun Mar 24 2024
Tonight - Snow changing to rain
The warm front will lift northward across the northern half of the
forecast area. The combination of 850 mb moisture transport and
isentropic lift will result in a snow band lifting northward across
the area. The 24.12z HREF continues to show that the hourly snow
rates in this band will likely (50-80 percent probabilities) exceed
1 inch per hour. These higher snow rates will likely over any given
area for up to a 2-hour period. As far as snow totals, they look
rather similar to the ones that we sent out yesterday. The only
changes were to north-central Wisconsin where the ranges look to be
coming in on the lower end of guidance.
The meso models and CAMS are in fairly good agreement that the
850 mb 0C isotherm will near the Interstate 90 around 25.01z,
Interstate 94 around 25.04z, and in Taylor County around 25.07z.
As this warmer air aloft moves northward the snow will
transition to rain.
Another shortwave trough will move northeast across the area during
overnight. This narrow band of precipitation will be in the form of
rain. Additional rain totals will be up to a tenth of an inch.
Depending on surface temperatures overnight, there may be some light
icing in north-central Wisconsin.
Monday and Monday Night - Scattered rain showers
A combination of 850 mb moisture transport and a series of weak
shortwaves moving northward will provide periodic showers. The
24.12z HREF 24-hour QPF ensemble mean is anywhere from a 0.25
and 0.75 inches, 0.5 to 1 inch for southeast Minnesota and
southwest and central Wisconsin, and between 1 and 1.5 inches
for Clark and Taylor counties in north-central Wisconsin.
With more showers expected, the high temperatures are slightly
cooler for Monday south of Interstate 94 with highs in the lower and
mid-50s. Meanwhile, there was very little chance for the rest of
the area with highs in the mid and- upper 40s.
Tuesday - Rain changing back to snow with little accumulations
expected
On Tuesday morning, a cold front will move east through the area.
Strong cold air advection it`s wake will cause temperatures to
slowly fall throughout the day. As this occurs, the wrap-around
moisture will gradually change over to snow. With this occurring
about 6 to 12-hours later than it looked yesterday, snow amounts
look to be anywhere from a dusting to a half-inch.
Tuesday Night into Wednesday - May be some scattered snow
showers in north-central Wisconsin
A 500 mb trough will remain across the Great Lakes. The combination
of cyclonic flow and low level moisture will keep skies mostly
cloudy north of Interstate 94. There may be just enough moisture in
Taylor County (north-central Wisconsin) for a maybe a few snow
showers. Confidence was not high enough to include these in the
forecast at this time.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1047 PM CDT Sun Mar 24 2024
Variety of flight conditions with larger storm system impacting
region at the moment. Where snow continues to fall, widespread IFR
to LIFR conditions prevail but VFR conditions were sweeping in from
the south as warmer air continues to advect in. This was not only
improving visibilties south of warm front but raising ceilings up.
Expecting general MVFR to VFR conditions for part of the night as
waves of precipitation move through but as entire wave approaches
and broad lift continues, expect ceilings to drop going through the
day Monday along with areas of fog as surface temperatures continue
to warm and snow melt adds moisture. Difficult forecast for sure
with so many variables but guidance certainly suggests higher
probabilities for IFR conditions at least later Monday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning until 1 AM CDT Monday for WIZ032>034.
Winter Storm Warning until 10 AM CDT Monday for WIZ017-029.
MN...Winter Weather Advisory until 10 PM CDT this evening for
MNZ086>088.
Winter Storm Warning until 1 AM CDT Monday for MNZ079.
IA...None.
&&
$$
UPDATE...Naylor
DISCUSSION...Boyne
AVIATION...Shea
Area Forecast Discussion
National Weather Service Cheyenne WY
600 PM MDT Sun Mar 24 2024
.KEY MESSAGES...
- Light to moderate snow is expected along the I-80 corridor
from Laramie to Cheyenne through early this evening. Localized
heavy banding is possible. Winter Weather Advisories are in
effect until 6 AM MDT Monday.
- Wind gusts 45-55 MPH are expected along the I-80 corridor
through tonight. Areas of blowing and drifting snow are
possible, especially west of Cheyenne.
- Much colder temperatures will arrive by late tonight, with
overnight lows 10 to 15 degrees. Sub-zero wind chills are
expected.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 216 PM MDT Sun Mar 24 2024
The main forecast challenge over the next 6 to 12 hours revolves
around the potential for banded snow over portions of south east
Wyoming, particularly from the Southern Laramie Range and points
southeastward into the I-25 corridor near Cheyenne. The high-res
model suite continues to show significant spread in QPF amounts,
with the potential for convective elements leading to an extreme
level of uncertainty at only ~3 hours lead time. A large area of
clearing was observed from 16-18z today, roughly along and south
of a line from Rock River to Pine Bluffs. This supported rapidly
increasing temperatures with daytime highs briefly reaching 55 F
at KCYS. This has supported rapidly steepening lapse rates, with
the help of strong 700-mb CAA overhead. Low-level instability is
plentiful with the latest SPC Mesoscale Analysis indicating 500+
J/kg SBCAPEs (50-100 J/kg 0-3 km CAPE) in this corridor. Intense
low-level convergence/frontogenesis along the frontal zone could
support banded snowfall along the I-80 corridor mainly from near
Elk Mountain eastward into Cheyenne/I-25. The past few HRRR runs
have suggested potential for 1-2 inch per hour snow rates across
the South Laramie Range/I-80 Summit area between 21z and 0z this
afternoon w/ total amounts well in excess of 6 inches using a 10
to 12 to 1 ratio. Some initial concerns regarding how quickly we
could see a change over from rain to snow with potential for the
cold air to lag a bit behind the initial frontal passage, but w/
the help of convective activity & resultant wet bulbing, surface
temperatures have plummeted from the middle 50s to middle 30s at
KCYS over just the past couple of hours. As winds increase post-
fropa, widespread gusts 45-55 MPH are anticipated this evening &
overnight. Fortunately, most of the snow should precede the high
wind gusts, but blowing and drifting snow impacts may linger for
a few hours into the night depending on the overall snow type as
temperatures continue to fall, and whether or not the fresh snow
pack will be particularly blowable. Even so there are sufficient
concerns for dangerous travel conditions due to black ice with a
potential flash freeze. In an earlier update, decided to issue a
Winter Weather Advisory for these aforementioned areas for total
accumulations possibly in excess of 3 inches beneath some of the
heaviest bands through the early evening. Admittedly though, our
confidence is quite low.
The rapidly deepening SE Colorado surface low will should bottom
out near 980 millibars late this afternoon before ejecting north
and east across central KS into eastern NE through 12z Mon. This
would normally be a favorable storm track for a significant snow
event for our CWA, but given the prior dry slotting which likely
resulted from the yesterdays northern short wave, this helped to
shunt the better moisture and dynamics further to the east. Wind
gusts will still become quite strong this evening and overnight,
especially along the I-80 corridor from Cheyenne to Sidney given
the very strong pressure gradients. Wind gusts up to 55 MPH will
be a good bet, though forecast soundings would suggest we should
be just shy of warning criteria. As such, we opted to cancel the
inherited High Wind Watch although a rogue 60 MPH gust still can
not be entirely ruled out. Concerning snow accumulations for the
western Nebraska Panhandle, still believe the best chance for 2-
5 inch accumulations will be found over the Pine Ridge in Dawes/
North Sioux counties & areas along the Cheyenne Ridge across the
southern Neb Panhandle. Turning much colder across all areas for
tonight, with lows 10-15 degrees and wind chills as low as -10 F
by sunrise Monday.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 216 PM MDT Sun Mar 24 2024
Minimal changes made from the previous forecast package. The primary
forecast concern in the long term forecast period will be the
generally unsettled pattern as shortwave passages and brief ridging
move through the forecast area, resulting in limited to low impacts.
Due to the brief shortwave passage Tuesday, isolated, weak rain/snow
showers cannot be ruled out across southeast Wyoming and western
Nebraska. The mountains have chances for light snow showers near
daily Tuesday through Thursday, but overall accumulations will be
minimal. As brief ridging takes over Wednesday into Thursday, CAG to
CPR pressure gradients jump up to near 50 meters, so gusty to strong
winds are possible, mainly in wind prone areas of southeast Wyoming.
During this time frame, temperatures will gradually increase each
day starting in the 30s to 40s Tuesday, increasing Wednesday to 40s
and 50s, then 50s and 60s Thursday and Friday. The next system is
forecast to start making its way into southeast Wyoming and western
Nebraska Friday into Saturday, so cooler temperatures and increasing
precipitation chances are likely. Long range guidance remains quite
variable from run to run, so confidence in impacts and timing
remains low.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 600 PM MDT Sun Mar 24 2024
Developing winter storm is currently located near the Colorado and
Kansas border. This storm is forecast to intensify as it lifts
northeast into southern Nebraska and northern Kansas. Thankfully,
the significant impacts for snow and blowing snow should remain over
central Nebraska with periods of impacts to Aviation for KSNY, KCYS,
KAIA, and KCDR at times through tonight.
HAZARDS/WEATHER TRENDS: Tricky forecast over the next 12 hours with
low confidence on timing of IFR (or lower) conditions. There is high
confidence that most of southeast Wyoming and western Nebraska will
see northerly winds gusting over 35 to 40 knots through most of
Monday afternoon. IFR conditions and light to moderate snow near
KLAR and KCYS should persistent through 02z before ending by 05z
late this evening. Can`t rule out additional bands of snow after
midnight (06z), but confidence is quite low at this time.
For the western Nebraska terminals, timing and intensity of snowfall
is highly uncertain, but the best time range for the heaviest snow
should be between 05z and 12z Tuesday. Lowered wind speeds a bit
with current models not initializing too well. The best chance to
see some blowing snow should be KAIA and KSNY overnight and early
Monday morning.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 6 AM MDT Monday for WYZ110-
115>118.
NE...Winter Weather Advisory until noon MDT Monday for NEZ002-095.
Winter Weather Advisory from 6 PM this evening to noon MDT
Monday for NEZ003-021-055.
&&
$$
SHORT TERM...CLH
LONG TERM...LEG
AVIATION...TJT
Area Forecast Discussion
National Weather Service Dodge City KS
701 PM CDT Sun Mar 24 2024
.KEY MESSAGES...
- Strong weather system will bring strong winds, fire weather,
and severe thunderstorms to our area today.
- Light snow will filter into our area behind a strong cold
front early Monday, lasting through much of the day.
- Hard freezes Tuesday and Wednesday morning with lows in the
teens to low 20s.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 130 PM CDT Sun Mar 24 2024
Water vapor satellite imagery and RAP upper air analysis
indicates a large, deep, longwave trough is in place over the
western CONUS, with an embedded shortwave trough rounding its
base over NM. Ahead of this wave, a sub-990-mb surface trough
has taken shape over eastern CO, with strong cyclonic flow
around it bringing 25-30 mph southerly winds with gusts of
35-40 mph to southwest KS. As the shortwave impulse ejects
northeastward towards the central plains, the surface low will
deepen further to near 980-mb, fostering increasing winds into
the 30-35 mph range with gusts of 45-50. Surface observations
show a dryline is extending south from the surface low near the
KS/CO border, which will mix east during the day today. Behind
this feature, plummeting dewpoints along with strong southwest
winds will support critical fire weather conditions, and a Red
Flag Warning remains in effect for all of far southwest KS until
01Z Monday. Ahead of the dryline, strong moisture advection via
southerly winds will draw low/mid 50s dewpoints poleward,
likely maintaining mostly cloudy skies over the warm sector,
resulting in a range of afternoon highs from the low 70s west to
low 60s east.
Focus now shifts to the potential for severe convection across
our area this afternoon and evening. Increasing forcing for
ascent ahead of the ejecting shortwave will aid in triggering
thunderstorms along the dryline around 20-21Z, which the latest
CAMs suggest will be near the US-83 corridor. Thermodynamic
profiles will be less than ideal given the aforementioned cloud
cover and meager moisture across the warm sector, but very cold
mid-level temperatures and steep lapse rates will support
MLCAPE on the order of 750-1250 J/Kg. On the other hand, wind
profiles will be more than sufficient for severe convection, as
35-45 kts of deep-layer shear will exist east of the dryline.
Current thinking is supercells and line segments will be the
primary storm mode, posing hazards of large hail up to 2" in
diameter, and damaging wind gusts up to 70 mph as storms race to
the northeast. A weak, isolated tornado cannot be ruled out,
but poor theta-e will be very difficult to overcome.
Sunday evening, thunderstorms will exit our area to the
northeast by around midnight.
Tonight, the upper level shortwave trough and attendant surface
cyclone will begin to pull away to the northeast, dragging a
cold front in its wake that will pass through the central
plains. Winds will flip to northerly behind the front, and
strong cold advection will transport much colder air into
southwest KS. Additionally, light wrap-around precipitation
will pour into our area early Monday, and swing across our area
through much of the day affecting roughly the northwest three
quarters of the DDC FA. Nearly all of this precipitation will
fall as snow, but accumulations are expected to be minimal as
HREF probability of snowfall exceeding 2" is less than 50% for
all areas except for a few small pockets over the west/northwest
zones. That said, with light snow and strong northerly winds,
blowing snow will be a factor, and winter weather headlines may
be needed.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 130 PM CDT Sun Mar 24 2024
Light snow may be ongoing at the beginning of the long term
period across the northeast zones, but this should clear out
fairly quickly leaving southwest KS precipitation free by or
shortly after midnight Tuesday morning. Medium range ensembles
suggest the upper level trough axis will cross the High Plains
overnight, and DNVA will begin to erode the cloud cover from
west to east across southwest KS. This along with weakening
northwest winds as the surface low drifts further away and fresh
snowpack will optimize radiational cooling, and a hard freeze
is expected Tuesday morning as temperatures nosedive into the
mid teens northwest to low 20s southeast.
Daytime Tuesday through the end of the period, ensembles
indicate weak upper level ridging will build across the western
CONUS through the end of the long term period, resulting in
generally quiet weather for southwest KS other than one more
hard freeze Wednesday morning. Expect afternoon highs to
increase from the 40s on Tuesday into the low 70s Friday, and
the mid/upper 70s by the weekend with no appreciable opportunity
for widespread precipitation.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 654 PM CDT Sun Mar 24 2024
Strong south to southwest wind will decrease in speed down to 15
to 20 knots sustained after sunset. There will be a 1 to 3 hour
period of fairly light wind late this evening before a major
cold front pushes in, immediately followed by a ramp up in wind
speed from the northwest at 25 to 30 knots sustained, gusts 35
to 40 knots. Upon the rapid increase in northwest wind will be
low stratus cloud yielding IFR flight category. IFR category
will persist through much of the morning along with light snow
reducing visibility to 1 to 3 miles, perhaps lower at times. If
enough snow accumulates (1"+), then blowing snow will also
reduce visibility even more, but the snow accumulation forecast
is fairly low confidence. Conditions are not expected to improve
much through the day Monday.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for
KSZ061-062-074>076-084>087.
&&
$$
SHORT TERM...Springer
LONG TERM...Springer
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1001 PM EDT Sun Mar 24 2024
.SYNOPSIS...
Dry and cool high pressure will persist across the area through
early Tuesday before a rainy cold front crosses the area late
Tuesday into Thursday. Dry and warmer weather returns Friday
through the weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 951 PM Sunday: Sprawling surface high remains centered over
southeast Canada this evening with ridging extending down the spine
of the Appalachians. A modest surface pressure gradient will support
light winds overnight with persistent dry/cool low-level advection.
High clouds will also stream across the region in advance of a broad
upstream trough across the Southern Plains with several embedded
shortwave troughs. Temperatures are still forecast to drop to around
or just below freezing roughly along and north of I-40 where a
freeze warning remains in place. If winds were to keep the boundary
layer mixed, combined with some degree of increasing cloud cover,
the coverage of sub-freezing temperatures may end up being more
limited in spatial extent. The frost advisory extending down to the
South Carolina state line also remains in place with the same
caveats from light winds and a mixed boundary layer. Sheltered
locations that decouple could still see patchy frost, however. Will
keep the hazard products going as is with only minor forecast
adjustments needed.
By Monday, the upper high pressure across the Gulf of Mexico
amplifies and begins to propagate eastward as the trough out west
also amplifies. This should aid in moisture return aloft by Monday
afternoon, priming the area for rain chances in the next period.
With more easterly surface flow, moisture return at the surface will
gradually increase toward the end of the period, but not before
another afternoon of low RH values and fire concerns once again.
Modeled soundings from the NAM and RAP show the stout mid-level dry
air remaining in place and a well mixed BL by Monday afternoon. Wind
conditions will be similar to Sunday, light winds and occasional
gusts, with gusts 30-35 mph at the higher elevations along the TN/NC
border. Temperatures Monday are expected to be warmer, with most of
the area east of the mountains reaching the upper 50s and low 60s.
&&
.SHORT TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 230 PM Sunday...As the forecast period begins Monday night,
the next weather systems to impact the region will be approaching
from the west as weak surface ridging persists across the forecast
area. A closed upper-low over the central Plains will deamplify
as it becomes absorbed into a more potent upper-level low across
south-central Canada, while a broad longwave trough dominates
the western two-thirds of ConUS. This system will be driving a
cold front across the Tennessee Valley Tuesday into Wednesday.
Light precip associated with this system will outpace the actual
front and will start to enter the area late Tuesday morning.
Meanwhile, a very weak low-pressure system embedded in the
southern jet will move across the Deep South, driving precip
response there. Therefore, the upper-level pattern evolves into a
broad southwesterly flow regime by the time these decaying systems
reach the southern Appalachians later Tuesday into early Wednesday
and we may lack the deep-layer forcing and notable moisture flux
necessary for significant rainfall during this time. This lack
of forcing and ongoing rainfall will allow the weak surface ridge
axis to persist along the foothills through Tuesday, resulting in
a low diurnal range on Tuesday across the far western Piedmont and
points west. In these areas, Tuesday morning lows will be near
normal but Tuesday`s highs will be 8-10 degrees below normal.
At this time, the wedge boundary is forecast to set up in the
vicinity of the I-85 corridor so the milder airmass east of the
wedge may result in highs just 2-4 degrees below normal, including
for the Charlotte metro.
The weak, southern stream low pressure system located over Georgia
Tuesday evening will make little progress eastward Tuesday night
thanks to shortwave energy rounding the base of the longwave
trough, which will amplify the trough over Texas and slow its
eastward propagation. Therefore, light rainfall and ample cloud
cover will persist over the forecast area into Wednesday morning,
keeping low temperatures about 6-8 degrees above normal area wide.
The northern stream cold front will finally enter the southern
Appalachians Wednesday morning but will have very little moisture
to work with as the low pressure system over Georgia starts to
respond to a new round of height falls over the Deep South and
slides into the Atlantic Coastal Plain, taking the best precip
response with it. The post-frontal northwest flow should help to
erode what is left of the persistent wedge for much of the area and
this combined with downsloping effects and decreasing cloud cover
should induce a notable warming trend for much of the forecast area.
Highs on Wednesday are currently expected to return to near normal
if not a few degrees above normal, especially across the mountain
valleys and Savannah River Basin. Highs may remain several degrees
below normal further north and east into the northern NC Piedmont,
where the residence time of the eroding wedge is expected to be
the greatest.
The aforementioned shortwave energy ejecting from Texas into the
Deep South will notably sharpen the bottom of the longwave trough
Wednesday night into Thursday. The trough will become neutrally
tilted by Thursday morning and possibly assume a negative tilt
overnight Thursday as the shortwave begins to lift north and east
over the Carolinas. This will cause deeper low pressure to develop
along the existing front, which is expected to be somewhere across
the lower Carolinas Wednesday night into Thursday. There has been
a lot of run-to-run variability across all model suites regarding
the exact frontal placement as a surface low moves up the front and
across the Carolinas on Thursday. Therefore, the forecast is of
lower confidence during this time as an axis of briefly moderate
to heavy rainfall is possible wherever the low track occurs.
At this time, however, the general consensus has been that the
best forcing and precip will be from the I-77 corridor and points
east, and we have higher confidence in lower rainfall amounts
the further west one looks, especially across the mountains.
There will be ample bulk shear but instability looks to be nearly
nonexistent at this time so heavy rainfall is the primary threat.
Expect highs to be slightly below normal given weak CAA on the
backside of the low track, cloud cover, and rainfall.
&&
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 230 PM Sunday...The long-term period will begin Thursday night
for this forecast package as the low-pressure system that impacts
the area during the short term is expected to rapidly lift off to
the east and north into the western Atlantic overnight Thursday
into Friday. High pressure over the Rust Belt will combine with the
intensifying coastal low to result in a notable pressure gradient
over the forecast area beginning Thursday night and persisting for
much of Friday. Gusty northwest winds may result depending on how
deep the low actually becomes. As a result, developing CAA in
the strengthening NW flow behind the low may allow temperatures
to get into the lower 30s over the mountains and mid- to upper
30s east for early Friday morning.
Nevertheless, the departure of this low will set up a nice
warming trend Friday and especially Saturday and Sunday, as high
pressure along the Gulf Coast slides off the Atlantic coast and
low-level southerly flow sets up underneath a flattened southern
stream ridge. Highs near- to slightly above normal on Friday will
rise into the lower 70s in the mountain valleys and mid-70s east
of the mountains on Saturday or about 7-9 degrees above normal.
As a fast-moving shortwave drops south into the Upper Midwest,
some guidance is suggesting that a warm front may activate from
the Tennessee Valley into the Ohio Valley later Sunday into early
Monday at the end of the period. However, confidence is low and
any precip impacting our area would be isolated and very light;
therefore it`s too early to consider introducing PoPs at this time.
Sunday`s highs may approach 80 east of the mountains and will
reach the mid-70s in the mountain valleys.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR conditions will prevail at all terminals
through the TAF period with high pressure dominating the weather
pattern along the East Coast. High clouds will stream across the
region through much of the period, but no restrictions are expected.
Winds will be out of the northeast outside of the mountains with a
southeast wind at KAVL.
Outlook: Rain chances and possible restrictions return Tuesday into
Wednesday as a cold front moves in. Lingering showers could keep
restrictions in place through Thursday.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Freeze Warning until 9 AM EDT Monday for NCZ035>037-056-057-
069-072-502-504-506.
Frost Advisory until 9 AM EDT Monday for NCZ068-070-071-082-
507>510.
SC...None.
&&
$$
SYNOPSIS...JMP
NEAR TERM...CP/TW
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...TW
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1104 PM CDT Sun Mar 24 2024
.KEY MESSAGES...
- There is an 80-90% chance that strong south winds will gust 45
mph or higher tomorrow to make travel difficult for high profile
vehicles on east-west roadways. Isolated gusts may exceed 50 mph
with rain showers.
- An axis of heavy rain will translate slowly east across the
region tomorrow evening into tomorrow night. While rain amounts
will vary considerably by location, west of the Illinois River
there is a 20-30% chance for more than two inches which could
result in localized ponding of water in poor drainage areas.
- There is a 50-80% chance for a hard freeze Wednesday morning
west of I-55 and Thursday morning north of I-70. Precautions
will be needed to protect early-season sensitive vegetation.
&&
.UPDATE...
Issued at 800 PM CDT Sun Mar 24 2024
Evening surface map showed deep 984 mb low pressure over southwest
KS. Tight MSLP gradient between this and 1032 mb high in SE Canada
was producing brisk southeast winds, which will continue to gust
up to 25 mph overnight. Regional radar mosaic indicated the
leading edge of warm conveyor precip streaming north over central
MO and much of IA. Short range guidance shows this making only
slow eastward progress overnight, and have kept higher PoPs
(30-60%) confined west of a Peoria to Springfield line through
sunrise. Thickening cloud cover and mixing provided by the
southeast winds will keep lows several degrees warmer than recent
nights, from 45-50F.
25
&&
.DISCUSSION...
Issued at 214 PM CDT Sun Mar 24 2024
Current visible satellite imagery shows mid to high clouds
continually streaming west-east across the Prairie State well ahead
of a deepening lee cyclone over the Western Plains. Southeast winds
of 17-22 mph are advecting a warmer airmass into the region this
afternoon, though until these winds become more southerly tomorrow
sfc moisture is not slated to increase a whole lot with dew points
upstream (IN, KY) in the upper teens to mid 20s. Winds are forecast
to gust to around 30 mph through this evening, easing a bit as we
decouple after around 7-8pm; still, the tightening gradient
associated with the approaching low pressure will lead to steady or
even increasing speeds (generally 18-25 mph) early Monday morning,
with gusts jumping up rapidly after about 7-8am.
The NAM and RAP agree a LLJ bringing 850-925mb winds to 45 to 55 kt
will slide east and into our area tomorrow morning, which will bear
watching when after sunrise our nocturnal inversion is eradicated
and mixing could bring some of those winds down to the sfc. The
24.12z HRRR suggests area-wide SSE gusts will rapidly increase to 40-
45+mph during the 7-9am time period, which seems reasonable based on
BUFKIT mixing techniques. While widespread cloud cover and
gradually eastward spreading rain should limit mixing potential
during the afternoon amidst the strong warm advection regime, HREF
mean suggests frequent gusts to 35+mph will continue, and the
aforementioned HRRR iteration - no doubt attempting to resolve
convective mixing - features pockets/bands of localized higher
gusts exceeding 55 mph (the most pronounced lifting north along
the leading edge of rain across our west). Concern only grows for
wind potential tomorrow evening when the LLJ reintensifies and
850mb winds increase to 60-75 kt east of I-55; any rain
showers/storms that can tap into this intense low level wind field
could mix severe (58+mph) gusts to the sfc, though HREF mean
suggests most locations (east of I-55) will gust mainly just into
the 45-50 mph range during this time. We`ve decided to go ahead
and issue a Wind Advisory to message this threat, and will handle
localized higher winds enhanced by convection with SPSs and/or
severe thunderstorm warnings, though anemic instability will keep
thunder pretty isolated.
Tuesday, we`ll need to watch for severe storms mainly across our
east where SPC has highlighted a marginal, level 1 of 5 (5 being the
highest), risk. As latest guidance doesn`t bring the true cold front
to even I-55 until roughly sunrise Tuesday morning, and both the
HRRR and NAMNest are bringing a low-topped wave of showers through
the area right along that front, small hail and gusty winds will be
a concern across at least the eastern half of the area...though the
threat does seem to increase for severe hail as the line moves east
and into a warmer/more unstable airmass across Indiana during the
late morning or early afternoon.
As far as precipitation totals go, HREF mean suggests the strong
warm advection from the LLJ will bring PWATs to well over an inch
area-wide, and with repeated rounds of showers depicted in every CAM
most, if not all, of central and southeast IL should have no trouble
getting over a half inch. NBM`s 10-90th percentile range suggests
most locations have an 80% chance for seeing precip totals between a
half inch and 2 inches, though north of a Macomb to Peoria line
there`s a 25-35% chance for more than 2 inches which could result in
some localized ponding of water in areas with poor drainage. With 6h
FFG at nearly 2.5 inches there, widespread flooding is not a concern
with this system, though we`ll keep an eye on things Monday
evening/night just in case.
We`ll cool off on the back side of this system Tuesday when 93%
(66%) percent of LREF members bring 850mb temps to sub -2 (-4) degC.
Given the lack of cloud cover expected behind the cold front,
efficient mixing will likely result in west wind gusts to 35 mph
Tuesday, bringing wind chills into the 20s during the evening. The
steep lapse rates driven by those cold temps aloft could also result
in some graupel showers and/or flurries Tuesday afternoon/evening,
reminding us that it`s still March - a month of extremes across the
Midwest.
Temperatures should warm back up late week, however, as ridging
across the Great Plains expands east. Differences in the
deterministic models speak some to variability in the ensemble
guidance as to how long the ridge sticks around before the next
trough digs in from the northwest, with NBM`s interquartile range
(IQR) extending from 62 to 77 degF in Lincoln on Sunday but 54 to 76
by Monday. This means that, assuming NBM is properly calibrated,
there is a 50% chance that the high temperature will verify within
that range, and 50% chance it will fall outside of it. In other
words, confidence is abnormally low in the forecast at that time
range, though middle of the road guidance (mid to upper 60s for
highs) is certainly trending above normal (upper 50s) on Easter
with a downward trend ensuing thereafter. Upwards of 70% of LREF
membership brings measurable precip to the region, with the
highest chances west of I-55, near the close of next weekend as
well, so it`s looking damp and possibly stormy.
Bumgardner
&&
.AVIATION... (For the 06z TAFs through 06z Monday Night)
Issued at 1104 PM CDT Sun Mar 24 2024
Strong, slow moving low pressure over the central Plains will
result in southeast winds gusting around 25 kt overnight. Deeper
mixing and a tightening MSLP gradient after sunrise will promote
even higher gusts to around 30-35 kt. A low level jet tonight will
bring marginal LLWS with winds at 2k feet near 50 kt, and another
low level jet Monday evening could bring LLWS to eastern IL
affecting KCMI.
A large north to south oriented rain band and associated MVFR
ceilings will begin to move into western IL after sunrise. The
system only slowly edges east through the afternoon, so -SHRA and
MVFR ceilings gradually spread east across the terminals from
18z-00z. Low MVFR conditions are expected Monday evening, with
low confidence (30%) that IFR conditions will develop.
25
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 8 AM Monday to midnight CDT Monday night for
ILZ027>031-036>038-040>057-061>063-066>068-071>073.
&&
$$
Area Forecast Discussion
National Weather Service Indianapolis IN
949 PM EDT Sun Mar 24 2024
.KEY MESSAGES...
- Partly Cloudy and breezy Tonight
- Gusty to windy conditions Monday-Tuesday, Wind Advisory in
affect 6PM Monday through 6PM Tuesday
- Moderate rainfall, few non-severe storms Monday Night-Tuesday
&&
.FORECAST UPDATE...
Issued at 944 PM EDT Sun Mar 24 2024
The forecast remains on track with only minor adjustments needed.
Quiet weather conditions are expected through the overnight
period as a dry airmass is still settled over the region. Current
observations show winds have tapered off slightly after sunset.
Look for winds to gradually pick up through tonight with a
tightening pressure gradient ahead of an advancing low pressure
system currently centered near southwest Kansas. Elevated winds
and increasing cloud cover will limit diurnal cooling. Expect
temperatures to remain in the 40s across most of the area tonight.
&&
.SHORT TERM (This evening through Monday)...
Issued at 308 PM EDT Sun Mar 24 2024
Rest of the Afternoon...
Temperatures are on their way to approaching normal late March highs
in the 50s. As is often the case, mixing has brought down lower dew
points and higher wind gusts than a model blend solution. Thus,
adjusted the grids to the lower HRRR dew points, which are close to
current observations, and also bumped up winds and gusts a few knots
as as plenty of sunshine has resulted in efficient mixing underneath
a 3K foot inversion. The combo of the gusty winds, low RH potential
and and marginal fuel moisture supports elevated fire danger which
is mentioned in the Hazardous Weather Outlook. For additional
details, see the Fire Weather section of this AFD.
Tonight...
Tightening surface pressure gradient ahead of a strong High Plains
system will result in a breezy night tonight, although winds may
briefly drop off at sunset before the gradient does tighten
sufficiently. Hi-Res soundings and satellite trends suggest high
clouds will be increasing late this evening and tonight as the
system gets close and upper flow becomes southwest. The increase in
cloud cover and breezy south and southeast winds suggest nighttime
lows will be in the late evening with steady or slowly rising
temperatures overnight.
Monday...
The Plains low pressure center will only gradually move east across
eastern Kansas on Monday. The breezy return flow will pump warmer
temperatures along with moisture in from the Gulf of Mexico. Would
not completely rule out a late day shower over the Wabash Valley,
otherwise, lack of a notable front or wave aloft in the fast
southwest flow, prefer to keep it dry through the day. BUFKIT
soundings suggest if any sort of mixing can occur outside of the
thicker clouds, winds could gust to near advisory criteria. With
moist low level advection occurring, the RH should remain high
enough for another elevated fire danger afternoon.
&&
.LONG TERM (Monday night through Sunday)...
Issued at 308 PM EDT Sun Mar 24 2024
By late Monday evening into the early overnight hours, rain and
gusty winds will quickly settle in from the west. With tight
pressure gradients and a strong mid to upper level jet overhead
gusts nearing 40 to 45 mph will be possible Monday night through
much of the day Tuesday. These winds have prompted a wind advisory
to start out the period which will last through Tuesday evening.
Within embedded storm cells there is a marginal chance of localized
severe winds being brought down to the surface and maybe some hail
within any stronger storms that may form. This threat is largely for
during the day Tuesday as daytime heating adds weak instability and
moderate lapse rates. Confidence on widespread severe threat is low,
but can`t rule out the isolated potential embedded within storms.
Main threat will be the non-thunderstorm winds blowing around loose
outdoor items. There will also be an isolated threat for brief
localized flooding Monday night when the bulk of the QPF is expected
to fall. In total, currently thinking there will be total QPF
amounts between half and inch and one inch across central Indiana.
Behind the initial system, surface high pressure will settle into
the area allowing for dry weather and calmer winds through the
end of the work week. Wednesday will be the coolest day of the
period with highs from the mid 40s to low 50s. Temperatures will
slowly warm through the remainder of the long term with highs in
the 60s to low 70s throughout Easter weekend. Some models show a
surface low tracking through the Great Lakes early in the weekend,
potentially bringing slight rain chances for the area Friday
night. A short wave shortly following may bring a better chance of
rain for the end of the weekend but there are uncertainties at
this time due to slight differences between models.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 741 PM EDT Sun Mar 24 2024
Impacts:
- Non-convective low level wind shear around 1500-1800 feet
03Z-15Z Monday
- Winds 120-160 degrees with occasional gusts around 18-24 knots
through 13Z Monday
- Winds 150-180 degrees to near 20 knots and gusts to around
30-35 knots after 13z Monday
Discussion:
Low-mid level dry air in place over the region will allow VFR
conditions to persist through Monday afternoon. Should only see some
cirrus increasing in southwest flow aloft. Mid and high end lower
clouds are possible Monday afternoon as moisture begins to stream in
ahead of an approaching low pressure system.
Non-convective LLWS is likely around 1500-1800 feet from 03Z
tonight through 14-15Z Monday morning. Breezy SSE winds will
continue through the TAF period and should increase on Monday.
Gusts around 30-35 kts are possible during the day Monday, mainly
near HUF/LAF.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 6 PM Monday to 6 PM EDT Tuesday for INZ021-
028>031-035>049-051>057-060>065-067>072.
&&
$$
UPDATE...Melo
SHORT TERM...MK
LONG TERM...KF
AVIATION...Melo
Area Forecast Discussion
National Weather Service New Orleans LA
331 PM CDT Sun Mar 24 2024
...New SHORT TERM, LONG TERM, AVIATION, MARINE...
.SHORT TERM...
(This evening through Tuesday)
Issued at 239 PM CDT Sun Mar 24 2024
No significant changes in thinking concerning the severe weather
risk across the area tomorrow afternoon into tomorrow night.
Conditions still look very favorable for severe storms to the
region and some of the severe storms will be capable of producing
tornadoes and strong damaging wind gusts. A review of HRRR and
HWRF model soundings indicates that conditions will be extremely
favorable for severe thunderstorms to impact portions of the
forecast area, and that the highest threat will be along and north
of the I-10/12 corridor. All of this will be driven by a strong
longwave trough ejecting out of Texas from Monday into Tuesday,
and taking on a more negatively oriented tilt as an upper level
jet streak rounds the base of the trough. A highly difluent
pattern aloft will form, and a broad region of upper level lift
will develop across the Lower Mississippi Valley by Monday
afternoon and evening.
In the low to mid-levels, the formation of a 60+ knot low level
jet will take place Monday afternoon and this LLJ will induce
extremely high shear values over the region through late Monday
night. Storm relative helicity values in the lowest kilometer will
exceed 400m2/s2 and effective bulk shear will approach 75 knots
over the northern third of the forecast area. This high shear will
combine with a moderate degree of MLCAPE nearing 1000 J/KG, that
forms as mid- level lapse rates steepen to around 6.5C/km, to
produce strong and deep rotating updrafts in the storms that
develop. Hodograph analysis from the model sounding data
also supports a multi-modal severe weather threat. There will be
a strong QLCS that forms along a pre- frontal trough axis
collocated with the strengthening LLJ, and several embedded
bowing segments and mesovorticies capable of producing tornadoes
and strong damaging wind gusts are expected within this QLCS.
Another concern will be the development of isolated supercells in
advance of the QLCS that will be capable of producing stronger and
potentially longer tracked tornadoes over parts of Southwest
Mississippi and the Florida Parishes tomorrow evening. It is
advised that everyone remain weather aware tomorrow due to this
significant severe weather threat.
Before this severe weather threat moves in, the other concern will
be strong onshore winds of 20 to 30 mph with higher gusts
affecting the area starting tomorrow morning and continuing until
frontal passage late Monday night. A wind advisory remains in
effect due to the threat of stronger gradient winds. The strong
onshore flow will also lead to some minor coastal flooding issues
in more flood prone areas of Hancock County and low lying eastern
shores of St. Tammany, Orleans, St. Bernard, and Plaquemines
Parishes. A coastal flood advisory is now in effect for these
areas.
After the front and severe weather threat moves east of the area
early Tuesday morning, conditions will quickly improve. Strong
subsidence and dry air advection behind the front will lead to
rapidly clearing skies and expect to see a very warm and sunny day
across the area by Tuesday afternoon. Continued deep layer west
to southwest flow and the subsident airmass will lead to decent
warming over the area. The latest runs of the NBM have begun
to pick up on this trend, and have stuck close to the NBM
deterministic output with highs in the upper 70s and lower 80s
across the area.
&&
.LONG TERM...
(Tuesday night through Saturday night)
Issued at 239 PM CDT Sun Mar 24 2024
No major changes from yesterday`s thoughts as we take over into the
long range beginning Tuesday night, as building CAA following a
recent cold front and severe storms. Clouds steadily clear out early
in the evening with winds remaining relatively elevated going into
Wednesday morning, enough to make for a chilly morning. Highs build
back into the 70`s Wednesday, with ample afternoon, deep PBL mixing
owing in a rather dry and breezy day. Chilly Wednesday night into
early Thursday as more of the colder continental airmass pushes into
our area, but SLP gradient remains tight owing in an overnight
breeze, mixing and reducing any maximized radiative cooling .
It wont be until Thursday night into Friday morning
when the surface high, clear skies and calm winds leads to optimal
radiational cooling causing the coldest morning. Latest long-range
guidance now pokes in the upper 30`s for northern areas with the
colder 25th percentile side of guidance, and will go ahead and keep
this lean going, emphasizing drainage basins. Only additional
modification was for Friday night/Saturday morning keeping it colder
for the eastern 1/2 of the area as the surface high lingers in
control of the region, with a chilly night for areas east of I-55
but steadily moderating from return flow for the Atchafalaya Basin to
the southshore, which will be the main story going into the weekend,
with highs building back into the 70`s and even well into the 80`s
while remaining dry into Sunday.
&&
.AVIATION...
(18Z TAFS)
Issued at 239 PM CDT Sun Mar 24 2024
VFR conditions will continue to prevail at all of the terminals
through the evening hours as a mid to high level cloud deck feeds
in from the west. At MCB, increasing winds just off the surface
could lead to a period of wind shear on the order of 40 knots
between surface and around 2000 feet above ground level during the
overnight hours. This is largely due to an inversion just off the
surface allowing winds to turn lighter at ground level. Tied into
this inversion, a lower cloud deck will also begin to develop at
GPT as warm and moist air moves over the cooler shelf waters just
offshore. Ceilings could fall into fuel alternate range of 1500 to
2000 feet by 12z. After 14z tomorrow, the weak inversion aloft
will mix out and stronger winds aloft will begin to mix down to
the surface. Sustained southeast winds in excess of 15 knots and
gusts over 30 knots at times can be expected at all of the
terminals. PG
&&
.MARINE...
Issued at 239 PM CDT Sun Mar 24 2024
A deepening low pressure system over the Plains will increase the
pressure gradient over the waters and lead to an extended period
of small craft and gale force wind conditions from tonight through
Tuesday morning. Conditions will begin to improve by Tuesday
afternoon as high pressure begins to move into the region. Winds
will increase to between 15 and 20 knots on Wednesday and Thursday
as a slightly cooler and drier airmass advects into the area
behind a reinforcing frontal boundary.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 58 77 58 79 / 0 60 90 10
BTR 63 79 60 79 / 0 60 80 10
ASD 62 77 61 80 / 0 40 90 30
MSY 65 78 64 78 / 0 40 80 20
GPT 62 74 62 81 / 10 30 80 50
PQL 60 73 62 80 / 10 20 80 60
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Wind Advisory from 7 AM Monday to 4 AM CDT Tuesday for
LAZ034>037-039-046>048-056>060-064>071-076>090.
Coastal Flood Advisory from 7 AM Monday to 4 AM CDT Tuesday for
LAZ069-070-076-078.
GM...Small Craft Advisory from 7 PM this evening to 7 AM CDT Monday
for GMZ530-532-534-536-538-550-552-555-557-570-572-575-577.
Gale Warning from 7 AM Monday to 4 AM CDT Tuesday for GMZ530-532-
534-536-538-550-552-555-557-570-572-575-577.
MS...Wind Advisory from 7 AM Monday to 4 AM CDT Tuesday for
MSZ068>071-077-083>088.
Coastal Flood Advisory from 7 AM Monday to 4 AM CDT Tuesday for
MSZ086.
GM...Small Craft Advisory from 7 PM this evening to 7 AM CDT Monday
for GMZ532-534-536-538-550-552-555-557-570-572-575-577.
Gale Warning from 7 AM Monday to 4 AM CDT Tuesday for GMZ532-534-
536-538-550-552-555-557-570-572-575-577.
&&
$$
SHORT TERM...PG
LONG TERM....KLG
AVIATION...PG
MARINE...PG
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
703 PM CDT Sun Mar 24 2024
.KEY MESSAGES...
* Three periods during which wind gusts may approach or exceed
45 mph are expected over the next 48 hours. The first is
Monday afternoon east of I-55 and south of I-80, second is
early Tuesday morning east of I-55, and third is Tuesday
afternoon areawide.
* Monday is looking primarily dry east of I-39, before widespread
rain moves across the area Monday night into early Tuesday
morning. A break in rain is expected toward daybreak Tuesday.
* A threat for severe thunderstorms continues to increase
Tuesday morning, especially east of I-55.
&&
.DISCUSSION...
Issued at 214 PM CDT Sun Mar 24 2024
Through Tuesday:
National satellite imagery augmented by RAP analysis and radar data
depict a sprawling low pressure system centered in far southeastern
Colorado well to the southwest of a surface high pressure system
centered in far southwestern Quebec. Waves of showers and a few
thunderstorms are parading within the warm conveyer belt of the
cyclone from central Oklahoma into central Iowa, southeast of a
burgeoning area of snow across the northern Plains. With a steady
feed of dry low-level air via breezy southwesterly winds on the
flank of the aforementioned high pressure system, our area is quiet
at this hour. Over the next 24 to 36 hours, the surface low pressure
system is expected to move through the Southern Plains and lift into
Upper Great Lakes leading to periods of inclement weather across
much of the central and northern United States. The latest and
greatest model guidance continues to advertise a later arrival of
the system locally, and is leading to modest changes in our
forecast.
First, as the low-level pressure gradient tightens overnight and
tomorrow, southeasterly low-level flow will gradually increase and
provide a reinforcing feed of dry air into the region. As a result,
mixing heights may be able to more readily build into the base of a
low-level jet after daybreak tomorrow, and lead to southeasterly
wind gusts of 35 to 45 mph especially east of I-55 and south of I-
80. At this point, the signal for frequent gusts over 45 mph during
daylight hours on Monday doesn`t currently look high enough to
justify a Wind Advisory (grand ensemble probabilities for gusts >45
mph are only 20-30% tomorrow afternoon), though our midnight shift
will be able to take another look. In addition, the feed of dry low-
level air may act as a wall to the eastward progression of the warm
conveyer belt precipitation tomorrow, effectively stalling rain from
moving east of I-39 through much of the day. For now, opted to
tighten up the gradient in PoPs across our forecast area to
advertise predominantly dry conditions east of I-39 and especially I-
55 through sunset.
Tomorrow evening, the surface low pressure system will begin lifting
northward into the upper Mississippi River Valley, pulling a plume
of 1"+ PWATs into northern Illinois and northwestern Indiana. An
ensemble of CAMs support the warm-conveyer belt of parading showers
finally shifting eastward, leading to high confidence (100% PoPs) in
rain for our entire area (especially from sunset to midnight Monday
evening). With cool-season forcing atop warm-season quality
moisture, efficient rain rates will lead to a swath of 1-2" of rain
somewhere across the region, seemingly favoring areas west of I-55.
In fact, any embedded convective element may allow for streaks of 2-
4" of rain, as suggested by 24-hour HREF LPMM. If such rainfall
amounts materialize, ponding in fields and typical low-lying spots
may occur. In addition, contingency forecasts that use the 95th
percentile GEFS QPF suggest several rivers may rise to bankfull where
rain is heaviest. For now, opted to issue a Hydrologic Outlook (ESF)
to highlight the threat for ponding in farm fields, low-lying spots,
and rises in river levels for all Illinois counties to account for
uncertainty in the exact placement of the band.
Early Tuesday morning (after midnight), ensemble model guidance has
started to hone into a threat for efficient mixing into the
strengthening low-level jet along the backside of the departing axis
of warm conveyer belt rain and as the surface low makes its closest
approach. Forecast BUFKIT profiles and HREF ensemble minimum and
mean wind gusts support gusts in the 45 to 55 mph range east of I-55
from around 3 AM to 10 AM Tuesday, and explicit HRRR/ARW output
suggests gusts may even approach 60 mph. Forecasting surface
nocturnal warm-advection wind magnitudes is always a challenge,
though conceptually this looks to be the type of scenario where
strong to locally damaging non-thunderstorm winds can occur. For
now, opted to only increase our gusts to around 45 mph in our
official forecast in favor of letting our midnight shift take
another look to consider a Wind Advisory for at least part of the
area.
After daybreak Tuesday, attention will turn to an apparently growing
threat for thunderstorms along the eastward-sweeping cold front of
the system lifting into Wisconsin. The most recently available high
resolution model guidance continues to advertise the northward
advection of a narrow tongue of low-level moisture ahead of the
front and a secondary upper-level shortwave early Tuesday morning.
Forecast soundings taken ahead of the front depict low-centroid
instability within a strongly sheared effective kinematic profile,
which are the hallmarks of low-topped supercell environments.
Perhaps most interestingly, 12Z CAM guidance is depicting a subtle
signal for a secondary surface low to develop along the cold front
in northern IL, leading to locally backed and augmented low-level
storm relative inflow. Taken together, the environment Tuesday
morning appears supportive of a band of low-topped supercells with a
threat for locally damaging winds and tornadoes. Based on the
current timing of the system and arrival/trajectory of the tongue of
low-level moisture, the highest threat for such a scenario appears
to be along and east of I-55 and further eastward into Indiana and
Michigan, though any continued slowing trend in the arrival of the
system would no doubt pull the threat for severe weather further
west. These types of severe weather scenarios are basically all or
nothing, and are entirely contingent on the quality of low-level
moisture. At this point, the SPC D3 Level 1/5 threat level outlook
remains appropriate though adjustments may be needed based on
observational trends going forward.
One final thing - Southwest winds will increase markedly behind the
cold front Tuesday afternoon thanks to deep mixing afforded by CAA
and stout pressure rises (on the order of 6-10mb/6 hours). As a
result, Tuesday afternoon will be yet another period to watch for
wind gusts approaching 45 mph across parts if not all of the
area.
Borchardt
Tuesday Night through Sunday:
High pressure will build over the area late Tuesday behind the
departing storm system which should clear thing up nicely for the
middle of the week. A tight pressure gradient on the backside of the
storm will keep conditions breezy for Wednesday, though not nearly
as windy as we`re expecting for Monday and Tuesday. Efficient cold
advection will keep highs stuck in the 40s area-wide on Wednesday. A
second center of high pressure focused to our southwest will take
precedence come Thursday and pump some milder air into the region.
The warm advection in conjunction with what should be a sunny day
will allow highs to return to the 50s on Thursday.
We`ll see steady height rises aloft Thursday night into Friday as an
upper ridge moves over the area. This will help pull us back into
the 60s for both Friday and Saturday. A mid level shortwave is
progged to spin up a surface low over the northern Plains on Friday.
The system`s warm front is slated to set up somewhere in the
vicinity of the CWA and most guidance is throwing up at least some
spotty showers in the area. This potential will carry on through the
weekend as the low pressure center and it`s trailing cold front work
across the region.
Doom
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 639 PM CDT Sun Mar 24 2024
- LLWS expected tonight
- Strong south winds expected to develop by mid morning Monday,
occasional gusts to 40kt possible mid morning into the
afternoon
- SHRA will develop at RFD during the morning, likely building
to a steady rain in the afternoon
- SCTD SHRA are possible at the Chicago terminals Monday
afternoon
Moderately strong and gusty east-southeast winds expected to
continue this evening. Frequency and magnitude of gustiness may
vary at times this evening with a tendency for frequency and
magnitude of gustiness to wane overnight. While OCNL gusts will
likely persist after 06Z, the frequency should decrease.
Meanwhile, winds will increase to 45-55kt around FL020 this
evening and continue overnight resulting in the potential for
LLWS.
After sunrise Monday, we should begin to tap into the slightly
weakening winds a couple thousand feet off the deck. As this
occurs, look for winds to turn more southerly (160-180) and
increase with frequent gusts 30-35kt by mid morning Monday and
continuing into the afternoon. There is a around a 40% chance
for some occasional south (160-180) wind gusts to 40kt by 15Z
Monday and potentially at times into the afternoon.
Rain is expected to mostly stay west of the immediate Chicago
terminals Monday, though likely impacting RFD. The rain should
eventually result in lower CIGS/VSBY at RFD by mid to late
afternoon. Immediate Chicago terminals (ORD, MDW, GYY, DPA) may
see some spotty showers Monday afternoon into the early evening.
More persistent rain should begin to impact immediate Chicago
terminals Monday evening.
- Izzi
&&
.MARINE...
Issued at 214 PM CDT Sun Mar 24 2024
Several periods of gale force winds may occur over the next 48
hours. Easterly winds will turn southeasterly and build this
evening to feature regular gusts to 25 to 30 kt. Southeast gusts
to 30 kt with a few gale force gusts to 35 kt can be expected
throughout the day on Monday. Tuesday, there is a signal that
more regular gale-force gusts to 35 kt may occur. For this
reason, a Gale Watch is in effect from early Tuesday morning
through Tuesday evening. Winds are expected to subside Tuesday
night. LMZ740 should see significant waves get up to around 10
ft tonight and again Monday night, and closer 6 to 8 ft across
LMZs 741 and 742 due to the southeasterly wind direction.
Doom
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 AM CDT Tuesday for Winthrop
Harbor to Northerly Is. IL.
Gale Watch from late Monday night through Tuesday evening for
the IL and IN nearshore waters.
Small Craft Advisory until 3 AM CDT Tuesday for Northerly Is.
IL to Michigan City IN.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Marquette MI
726 PM EDT Sun Mar 24 2024
.KEY MESSAGES...
- Late season winter storm lifting northeast from Colorado brings
accumulating snow and hazardous travel this afternoon into Monday.
- Gales are expected across Lake Superior Monday into possibly
Tuesday.
- Westerly lake effect snow develops early Wednesday morning and
continues through Thursday evening, mainly across the Copper Country.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 357 PM EDT Sun Mar 24 2024
RAP analysis has a deepening surface low over eastern CO this
afternoon, with tight southerly flow out ahead of it leading to
robust WAA into the Great Lakes. A strong 40-55kt 850mb LLJ is
draped across the Plains, with the exit region directed northeast
IA. Light snow has spread into the Great Lakes with modest WAA and
isentropic ascent. However, the steadier snowfall remains well to
our southwest so far, across central MN to western WI on the nose of
the jet. Will note a heavier band moving through northern IA at this
time where 850mb frontogenesis is maximized. There are also a couple
of prominent dry slots noted on water vapor imagery; the first is
working through SW MN behind the leading swath of steady snowfall,
and the second moving northward through eastern IA behind the narrow
band of heavier snow.
Weak radar returns are apparent across the UP, with plenty of ASOS
sites reporting snow on and off as well as brief drops in
visibility. So, expect flurries and light snow to continue the rest
of the afternoon before steadier snowfall starts to move in just
before 00Z. Guidance remains in fairly good agreement on QPF amounts
up to a tenth of an inch by 00Z, highest along the WI border; with
SLRs still around 14:1, this should result in a quick half to 1.5 in
of snow into the evening.
Steadier snowfall arrives after 00Z as the stronger ascent reaches
the area. HREF snowfall rates continue to favor widespread quarter-
to half-inch per hour snowfall rates across the central and western
UP from around 00-09Z, and several hours of higher rates up to 1-
1.5in/hr from around 03-08Z as the heavier band currently moving
through IA on the back edge of the main precip shield arrives.
Simulated reflectivity does indicate that this band washes out
somewhat while lifting through WI, with only around a 40% chance of
those higher snowfall rates being realized as the band pivots into
the UP. Snow quickly tapers off across the eastern UP the second
half of the night as the warm front lifts to the NW and the dry slot
moves in from the southeast, but snow will continue across the far
western UP. SLRs remain quite low with a narrow DGZ up above 10kft
in soundings, and quite warm (though sub-freezing before 12Z)
profiles. Ratios starting off around 10-14:1 before 06Z begin to
fall below 10:1 the second half of the night. With widespread QPF
amounts up to a quarter to half an inch to the west, and up to a
quarter inch in the east, we should be looking at snow totals
generally around 4 to 8 inches for much of the western UP. Higher
embedded amounts up to 10in are possible particularly throughout the
Keweenaw, where colder profiles lead to higher SLRs. Lighter snow
totals around 1-3in are expected across the eastern UP. With no real
major changes to the timing and snowfall totals, our current
headlines will remain intact.
Otherwise, expect temperatures to largely hold steady overnight,
hovering in the upper 20s to lower 30s. Stable soundings indicated a
limited potential for us to tap into the stronger winds arriving
aloft tonight, but we could still see some 20mph gusts heading into
the second half of the night.
&&
.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 316 PM EDT Sun Mar 24 2024
The long-term forecast starts off continuing the precipitation
across the area due to the vertically-stacked low lifting through
the Plains towards western Lake Superior. While we will likely see
some snow initially over the western half of the U.P., with the warm
nose continuing northwards across the area throughout the day,
expect the progressive transition over to rainfall from the
southeast to northwest throughout the day Monday. In addition, some
recent CAMs such as the 12z HRRR are highlighting the dry layer in
the lower levels being stronger and moving a little further west
than previously anticipated. Thus, precipitation chances look to be
fairly limited (around 10 to 40% chance) Monday morning into early
Monday afternoon over the eastern half. As we see the transition
from snow to rain across the area Monday, we could see a wintry mix
of sleet and freezing rain Monday morning into Monday afternoon over
the higher elevations of the western U.P. in-between the snow and
rain. While a subtle shortwave lifts around the vertically-stacked
parent low towards our area late Monday, with the dry slot in the
lower levels `eating away` much of the precipitation potential,
icing and sleet accumulations look to be fairly minimal. Indeed, by
the time some of the CAMs show freezing rain over the higher
elevations over the western U.P., there is a diminishing window of
negative energy near the surface in comparison to a growing layer of
positive energy aloft within the atmosphere. Thus, with surface
temperatures likely to be near freezing already, the sun being out
(although cloud covered), and with an ever shrinking negative energy
layer overhead, I`m thinking icing accumulations will be no more
than a glaze and mostly on elevated surfaces and the snowpack that
will have developed by then. That being said, it could make for an
extra slick spot here or there on the untreated roadways across the
higher elevations, particularly the Keweenaw where the colder
temperatures are looking to hold on the longest.
Moving into Monday night and Tuesday, expect pure rainfall across
the area as we will reside in the warm-sector of the parent low by
then. Two shortwaves look to rotate around the parent low Monday
night through Tuesday, with the first shortwave bringing light to
occasionally moderate rainfall at times, particularly over the
western U.P. where a local deformation band could set up. In
addition, some locally higher rainfall rates could be seen near Lake
Michigan due to some slight upslope flow that could occur. Behind
this shortwave, the second shortwave looks to lift up into the area
Tuesday and bring some additional light rainfall across the area
(there won`t be as much moisture available in the atmosphere by
then), save for the south wind lake-effect belts over the eastern
U.P.; this area could see some locally moderate rainfall at times as
a deformation zone could enhance the rain rates. By the late
afternoon Tuesday, the cold air advection behind the parent low
begins to work its way into our far west by Ironwood, transitioning
any remaining rainfall back over to snow showers through Tuesday
night.
As the parent low continues lifting through northern Ontario
Wednesday, some lake-effect/enhanced snow showers are expected
across mainly the west snow belts as delta Ts across Lake Superior
drop to the upper teens to around 20C behind the wake of the low. In
addition, there is a chance (30%) that some scattered snow showers
will traverse from west to east across the interior areas of the
U.P. Wednesday if the comma-head of the low is south enough to be
over us during the day. While only light snowfall is generally
expected for the area, we could see some locally higher snow totals
across the Keweenaw as some of the medium range guidance hint at a
possible (30%) convergent band setting up over the area. A secondary
shortwave low rotating around the parent low looks to keep the lake-
effect snowfall over the west snow belts going late Wednesday night
through Thursday. As ridging builds into the region Thursday night
into Friday, expect the lake-effect snowfall to slowly end from west
to east while transitioning to the northwest snow belts.
Moving into next weekend, expect temperatures near normal. While we
could see an additional shot for precipitation sometime during the
weekend, with model guidance kind of being all over the place right
now, the confidence in precipitation chances is rather low at this
time (around 30-ish% chance).
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 726 PM EDT Sun Mar 24 2024
Snow will continue overnight with IFR conditions expected at all
sites. IFR conditions will last through the period at IWD. IWD could
also briefly see some freezing rain Mon morning before a rain and
snow mix occurs before becoming all rain by late Mon afternoon. At
CMX, LIFR will move in by Mon afternoon with snow changing over to
rain by mid afternoon. At SAW, dry slot comes in later tonight and
snow will end and conditions will go VFR late tonight. Rain moves
back in at SAW by Mon afternoon and will go back to IFR.
&&
.MARINE...
Issued at 316 PM EDT Sun Mar 24 2024
East to southeasterly winds are increasing this afternoon through
tonight as a warm front moves into the Upper Midwest, with winds
reaching speeds of 20 to 30 knots by midnight tonight. As the warm
front begins moving into Lake Superior tonight into Monday, winds
slowly continue increasing, with some gale force gusts being seen
from time to time during the morning hours along the International
Border and western lake as some mixing occurs within the first 500
to 1000 feet up from the surface. As the mixing continues and the
warm front continues advecting over Lake Superior, more consistent
gales of 35 to 40 knots begin occurring by the afternoon hours
Monday. As the parent low begins lifting towards western Lake
Superior Monday night into Tuesday, the winds over the western half
of the lake begin to back to the northeast and weaken. Meanwhile,
some of the CAMs are showing some sharp increases in the wind gusts
along the International Border to Whitefish Bay Monday night into
Tuesday morning, especially the Hires-FV3 and the HRRR. While I do
have my reservations due to mixing likely (70% chance) being limited
due to the temperature inversion just above the surface by this
time, if the funneling due to a convergence of the winds is strong
enough, some gales are certainly possible (50% chance). As the low
continues into northern Ontario Tuesday evening, the southeasterly
winds over the eastern lake weaken whereas cold air advection behind
the low will increase winds to generally 20 to 30 knots from the
northwest over the west half. As cold air advection continues to
spread across the lake into Wednesday, winds back to the west at
around 30 knots. That being said, some gales up to 35 knots are
possible (40 to 50% chance) near the Keweenaw Wednesday. A secondary
shortwave low rotating over Lake Superior Wednesday night into
Thursday looks to keep westerly winds of 20 to 30 knots going. By
Friday, the winds are projected to weaken to 20 knots or less as
ridging moves back across the Upper Great Lakes.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Warning until 2 PM EDT Monday for MIZ001-003.
Winter Weather Advisory until 2 PM EDT /1 PM CDT/ Monday for
MIZ002-004-005-009>012-084.
Winter Weather Advisory until 5 AM EDT Monday for MIZ006-013-
014-085.
Lake Superior...
Small Craft Advisory until 11 AM EDT Monday for LSZ244.
Small Craft Advisory until 8 PM EDT Tuesday for LSZ245.
Gale Warning from 8 AM EDT /7 AM CDT/ Monday to 2 PM EDT /1 PM
CDT/ Tuesday for LSZ162-263.
Small Craft Advisory from 8 AM EDT /7 AM CDT/ Monday to 8 PM
EDT /7 PM CDT/ Tuesday for LSZ240-241.
Small Craft Advisory from 8 AM to 8 PM EDT Monday for LSZ242.
Small Craft Advisory from 2 AM Monday to 8 PM EDT Tuesday for
LSZ243.
Gale Warning from 11 AM Monday to 2 PM EDT Tuesday for LSZ244-
264.
Small Craft Advisory until 2 PM EDT Tuesday for LSZ246>248.
Small Craft Advisory from 5 AM to 2 PM EDT Monday for LSZ249-
250.
Small Craft Advisory until 2 PM EDT Monday for LSZ251.
Gale Warning from 2 PM Monday to 2 PM EDT Tuesday for LSZ251-
266-267.
Lake Michigan...
Small Craft Advisory until 11 AM EDT Monday for LMZ221.
Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for LMZ221.
Small Craft Advisory until 8 PM EDT Tuesday for LMZ248-250.
&&
$$
SHORT TERM...LC
LONG TERM...TAP
AVIATION...07
MARINE...TAP
Area Forecast Discussion
National Weather Service Morristown TN
1033 PM EDT Sun Mar 24 2024
...New UPDATE...
.UPDATE...
Issued at 1022 PM EDT Sun Mar 24 2024
Most locations in the valley tonight are running warmer than
expected, thanks to a slight breeze helping to mix down warmer
air. Those with calm winds have been running on track. Mixed in
some RAP model guidance into an NBM and observations blend to
raise temperatures a few degrees through the remainder of the
night. Winds will stay light in the valley tonight, outside of a
few errant gusts. Winds are expected to strengthen in the
mountains and foothills overnight, and the weather station in
Camp Creek has begun to record 30 to 35 mph wind gusts this
evening, on track with the forecast.
&&
.SHORT TERM...
(This evening through Monday)
Issued at 230 PM EDT Sun Mar 24 2024
Key Messages:
1. Dry for the short term period.
2. Winds will become strong and gusty in some of the mountains and
foothills of the E TN mountains tonight and Monday.
3. Low RH values expected Monday afternoon, and this will combine
with the strengthening winds to elevate fire weather concerns
especially to the lee of the mountains.
Discussion:
We start the period with surface high pressure centered to our
northeast and a low pressure system over the western Plains. This
low pressure system will track slowly east across the central Plains
during the short term period. Out ahead of this system, a low level
southeasterly jet will strengthen over our area. While moisture will
be slow to move in and the short term period will be rain free, the
set up looks favorable for mountain wave wind enhancement to occur
in the usual higher elevation and foothill areas starting tonight
and continuing through the short term period. Right now it looks
like we will see gusts to around 50 mph at times later tonight into
Monday in the usual areas, and the winds may begin to strengthen
further late Monday afternoon. Will issue a wind advisory starting
at midnight tonight in the E TN mountains, with a high wind watch
beginning late in the day.
In addition to the wind, RH values will get quite low Monday
afternoon with many areas dipping into the 20s. This will increase
the fire weather danger especially in the areas that see gusty winds
on the leeward side of the mountains. After coordinating with TN
state forestry, no fire weather watch will be issued at this time
given the recent rain and rapid greenup that is occurring. However,
later shifts will continue to monitor and at least a fire danger
statement may be issued closer to the time of the winds/low RH
combo. For now will headline these conditions in the FWF.
&&
.LONG TERM...
(Monday night through next Sunday)
Issued at 230 PM EDT Sun Mar 24 2024
Key Messages:
1. Mountain wave wind event expected to strengthen Monday into Tuesday
2. Showers and isolated thunderstorms are expected off and on
Tuesday through Tuesday night with shower coverage decreasing on
Wednesday.
3. Near freeing temperatures possible Friday morning.
Discussion:
By Monday night the incoming frontal boundary will be moving near
the Mississippi river as the Tennesee Valley will likely remain well
north of the warm front, waiting for the occluded frontal boundary
to move in. Along and ahead of this system a very strong LLJ will
bring impactful weather to start the work week. Biggest impact will
likely be breezy conditions Monday night through Tuesday as core of
the jet looks to increase above 70 knots in northern TN and central
KY. This jet being out of the south to southeast will induce a very
strong mountain wave effect for multiple days, peaking in strength
late Monday into early Tuesday. Orientation of the jet, strength of
the jet, and inversion in the lower levels all point towards a
strong wind event. Based on latest high resolution guidance am
expecting multiple reports of 60+ mph winds and cannot rule out
seeing gusts over 80 mph in some locations. With this in mind will
issue a High Wind Watch for the southern Appalachian Mountains and
foothills Monday afternoon through Tuesday afternoon. Elsewhere
expect conditions to be breezy in the valley, and especially along
the Cumberland Plateau, with winds possibly gusting over 45 mph on
Monday into Tuesday. Further down in the valley it wont be nearly as
strong, but still expect fairly stout winds most of the day on
Monday into Tuesday, especially along ridge tops and higher
elevations.
Besides the wind the other impact will be widespread showers Tuesday
morning into Wednesday morning as the front sweeps through. Cannot
completely rule out seeing a few rumbles of thunder (with the
highest chances occurring across southeast TN) but expect most people
will just see light to moderate rainfall. Most places will see less
than an inch of rain over 24-36 hour event, but some places south of
Interstate 40 could see storm totals over an inch.
Once the front finally sweeps through we`ll see broad troughing into
Thursday with near freezing tempos Friday morning under clear skies
and calm winds. Friday morning could see frost develop especially
along and north of Interstate 40 for a few hours before sunrise.
Strong ridging and surface high pressure will quickly warm things up
to end the work week and the upcoming weekend is shaping to up to be
fairly pleasant with mostly sunny skies and temperatures in the 70s
&&
.AVIATION...
(00Z TAFS)
Issued at 740 PM EDT Sun Mar 24 2024
VFR through the TAF period for all sites with scattered to broken
high clouds aloft, still think LLWS will be borderline at CHA.
Winds are expected to be light overnight, winds will increase
again at CHA at daybreak and remain gusty through the remainder of
the period. Otherwise a strengthening mountain wind event will
contribute to southeasterly flow at TYS and TRI.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 47 61 52 62 / 0 0 60 90
Knoxville McGhee Tyson Airport, TN 42 64 50 63 / 0 0 30 90
Oak Ridge, TN 42 66 49 63 / 0 0 40 90
Tri Cities Airport, TN 38 64 45 61 / 0 0 10 80
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 5 PM EDT Monday for Blount Smoky Mountains-
Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-
Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi.
High Wind Watch from Monday afternoon through Tuesday afternoon
for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-
Sevier Smoky Mountains-Southeast Carter-Southeast Greene-
Southeast Monroe-Unicoi.
VA...NONE.
&&
$$
SHORT TERM...Wellington
AVIATION...Wellington
Area Forecast Discussion
National Weather Service Omaha/Valley NE
644 PM CDT Sun Mar 24 2024
.KEY MESSAGES...
- Widespread rain expected through this evening with
thunderstorms possible. A few could be strong this evening and
overnight near the Nebraska/Kansas border. Additional strong
to isolated severe storms will be possible in far eastern
Nebraska and southwest Iowa Monday afternoon.
- We`ve converted the Winter Storm Watch into a Winter Storm
Warning and added a Winter Weather Advisory for line of
counties to the east for Monday.
- A band of mixed precipitation followed by heavy snow will
clip portions of northeast Nebraska Monday (40-70% chance of
at least 4 inches in Knox/Antelope Counties). Combined with
wind gusts of 35 to 45 mph, whiteout conditions and
significant travel impacts would be possible.
- A second, slightly lighter band of snow may bring travel
impacts to areas farther east of the main band Monday evening
into Tuesday (40-60% chance). Highest chances would be in
vicinity of Norfolk (within a county or 2).
- Dry weather returns for Wednesday and Thursday with
temperatures trending back up into the 60s by Thursday into
the weekend. &&
.DISCUSSION...
Issued at 358 PM CDT Sun Mar 24 2024
Today through Tuesday Morning:
Water vapor imagery this afternoon continues to feature the deep,
positively-tilted trough over the western half of the CONUS serving
as the catalyst for the busy short-term forecast. A recent surface
map places a deepening surface low over the midpoint of the
Colorado/Kansas state line, with a lifting warm front extending east-
northeast across south-central Nebraska into eastern Nebraska and
southwest Iowa. A sharp gradient in surface temperatures has set up
locally, with temperatures in eastern Nebraska climbing into the 50s
while central and parts of northeast Nebraska continue to hover
around freezing. Widespread forcing for ascent aided by strong warm
air advection and PVA are resulting in scattered rain, which is
expected to continue in waves in eastern Nebraska and Iowa, while
Northeast Nebraska sees it continue somewhat continuously through
tomorrow morning. Somewhat steep lapse rates in the mid-levels will
likely result in thunderstorms, with a 5 to 10% chance that we see
quarter-sized hail or a damaging wind gust near the KS/NE border
this evening.
During the overnight hours, continued frontogenesis and surface cold
air advection will push the freezing line into northeast Nebraska
around 2 to 4 AM. Along this line, liquid rainfall will transition
to a heavy wintry mix of rain, snow, sleet, and freezing rain due to
a warm isothermal layer in the low-levels and then eventually into
heavy snow to the west. There`s still wiggle room for temperatures
based on the latest model guidance, but the general trend has been
for colder temperatures to push in earlier based on p-type and
temperature trends in the HRRR as an example. This line will
continue pushing east through the morning while east of it will see
a lull in rainfall, before the line pushes farther eastward and
precipitation increases once again Monday afternoon and evening. As
Monday night goes on, the arm of snowfall will become more ragged
and lower dramatically in coverage. Despite this, much of
Nebraska and Iowa will see some snowfall (even through many
will struggle to see a dusting) by daybreak Tuesday. Strong
winds will follow behind that freezing line, with gusts of 35 to
45 mph continuing into through around noon Tuesday.
As far as snow totals go, the eastward trend in cooler temperatures
and the mixed precipitation line in model guidance nudges us to
increase snowfall totals in northeast Nebraska, with Knox and
Antelope Counties seeing at least the some western portions see 6
inches of snow in addition to some ice. Confidence in the blowing
snow further limiting visibility during the peak snowfall has
decreased due to the character of it being generally heavy and wet,
but we are still very close to blizzard conditions. In the meantime,
we`ve converted the Winter Storm Watch to a Warning, and added a row
of counties to the east of it into a Winter weather Advisory with
the combination of up to 2 inches of snow and some ice. Those
outside of the advisories or warnings will likely see less than an
inch, but could still see slickness for the Tuesday morning commute.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 617 PM CDT Sun Mar 24 2024
Currently, MVFR ceilings across much of southeast Nebraska and
southwest Iowa (KOMA and KLNK) give way to IFR/LIFR ceilings
and visibilities further northwest into northeast Nebraska
(KOFK). These low ceilings are expected to persist across the
region throughout the entire forecast period with the lowest
ceilings expected sometime between 09Z and 18Z. Surface winds
across southeast Nebraska and southwest Iowa (KLNK and KOMA)
have continued to strengthen this evening. Wind gusts up to 35
knots will be possible through 12Z, though more conservative
wind gusts have been put into the TAFs for prevailing groups.
Waves of precipitation are expected to traverse the forecast
area southwest to northeast throughout the duration of the
forecast period impacting all TAF sites. Thunderstorms ongoing
across Kansas and south-central Nebraska are expected to develop
northeastward and bring the risk for lightning at all TAF
sites. The most likely times of arrival for thunder at TAF sites
are listed below
KOMA: 11Z
KLNK: 04Z
KOFK: 09Z
Thunderstorms will end first at KOFK and KLNK by 12Z, and at
KOMA by 17Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning from 4 AM Monday to 7 AM CDT Tuesday for
NEZ011-016.
Winter Weather Advisory from 7 AM Monday to 7 AM CDT Tuesday
for NEZ012-017-030-031-042.
Wind Advisory until 10 AM CDT Monday for NEZ088>093.
IA...None.
&&
$$
DISCUSSION...Petersen
AVIATION...Darrah
Area Forecast Discussion
National Weather Service Pocatello ID
859 PM MDT Sun Mar 24 2024
.UPDATE...
Cold front has stalled across the eastern Magic Valley into the
lower Snake Plain. Showers along the front have been slow to
diminish this evening. The 00z NAM and the HRRR even indicate that
we may not completely rid ourselves of showers late in the night.
Updated forecast to keep low chances of showers near the front
through the night.
13
&&
.PREV DISCUSSION... /issued 207 PM MDT Sun Mar 24 2024/
SHORT TERM...Tonight through Monday night. Satellite imagery
shows deep trough over the Western US with trough axis neatly
overhead East Idaho early this afternoon, and shortwave axis
sliding south through the Idaho panhandle. Radar imagery shows
widespread shower activity across the region. Snow levels are
widely varying between 5500 and 6500 ft. Given the convective
element and mild snow levels, not expecting significant
accumulations through the remainder of the day. 90th percentile
snow amounts focus up to 6 inches of accumulation across a few
ranges in the southern highlands, but in general believe this to
be over done and expect amounts closer to the means up to 3
inches. Much of the lower and mid level cloud cover should
dissipate with the loss of daytime convective influence, leaving
just high cloud the concern for the overnight. Given the recent
upgrade to G4 magnetic storm levels by the Space Weather
Prediction Center, that could mean potential aurora viewing
overnight, if the clearing can be realized! Best chances appear to
be from Blackfoot to Island Park at this time.
As the panhandle shortwave drops through the state during the day
Monday, expect another round of showers. Temperatures should be a
few degrees colder, so more valley areas will be subject to seeing
snow. Similar to this afternoon, however, amounts are not expected
to be significant, so will continue to forego issuing any
headlines. DMH
LONG TERM...Tuesday through next Sunday.
The extended period will be an active one with rain/snow chances
almost daily and temperatures running within a few degrees of
normal. Lingering showers will continue on Tuesday as the departing
trough continues to lift across the central U.S. Snow levels will be
low enough to support snow to valley floors. A transient ridge will
move through on Wednesday, allowing for a break in the active
pattern with mostly dry conditions outside of slight chances for
showers over the central and eastern mountains. Heading into
Wednesday night, the next potent upper low will be advancing toward
the west coast with the National Blend carrying widespread PoPs of
60% to 95% again on Thursday. Models show the low rotating southward
along the coastline, reaching the southern CA coast by next weekend.
As it tracks south, southwest flow aloft will filter the bulk of
moisture into Southeast Idaho on Thursday. Warmer temperatures will
mean mostly rain for locations below 6,000 feet elevation throughout
the remainder of next week. NBM 24-hour snowfall probabilities of 3
inches Tuesday morning through Wednesday morning only runs 10% to
25% across the highest peaks of the central and eastern mountains
with up to 45% chance across the Bear River Range. Cropp
AVIATION...
Isolated rain and snow showers will continue throughout the period
with predominately VFR conditions forecast. However, heavy
rain/snow, degraded VIS and CIGs, gusty winds, and lightning could
accompany any convectively enhanced bands of precipitation. HREF
probability of thunder is highest near KBYI, KPIH, and KSUN, where
chances range around 5-35% this afternoon and evening. Cropp
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$